Butterfly valve

ABSTRACT

Provided is a butterfly valve that prevents occurrence of erosion, thereby rendering it possible to secure fine adjustment of a volumetric flow rate of a fluid in an area of low degree of valve opening or in an area of minute degree of valve opening, to infallibly attain high range ability. This invention provides a butterfly valve for opening and shutting an interior of an elastic seat ring  2  mounted in a cylindrical valve casing  1  by rotation of a disc valve member  3,  wherein the butterfly valve comprises depressing valve parts  10  and  11  provided at least on an orifice side  8  of the valve member  3  and adapted to make depressing contact with the elastic seat ring  2  in the area of low degree of opening or in the area of minute degree of opening of the valve member  3,  a void part  12  formed along an outer peripheral edge of the valve member  3  or at a downstream side position of the outer peripheral edge, and communicating parts  13  formed in the valve member  3  or the depressing valve parts  10  and  11  to establish communication from the void part  12  toward a downstream side.

TECHNICAL FIELD

This invention relates to butterfly valves of the type possessing afunction of establishing tight shut and preventing itself fromdeveloping erosion as a matter of course, and enabling even a minuteflow volume to be duly adjusted particularly in the area of small degreeof opening or the area of minute degree of opening and exhibiting aprominent effect in high range ability.

BACKGROUND ART

Butterfly valves, on account of distinctions, such as simplicity ofstructure, lightness and low operating force, are being used as stopvalves or, depending on purposes of application, as flow volumeadjusting valves. Particularly when such a butterfly valve is used as aflow volume adjusting valve, it has the possibility of not onlygenerating cavitation on the downstream side of the valve member to emitvibration and noise but also inducing the so-called erosion, namely thephenomenon of the valve member and the adjunct piping yielding to damageand corrosion.

With the object of solving these problems, various countermeasures havebeen proposed.

JP-A SHO 57-157866, for example, discloses a method for repressing thecavitation which would occur on the downstream side of the valve memberby providing the outer peripheral edge of the valve member with spacedprojections resembling the teeth of a comb and causing the projectionsto transform a fluid into a jet. JUM-A SHO 62-6568 discloses a methodfor rectifying the turbulence of a fluid by providing the opposite outerperipheral parts of a valve member each with a belt member and forming agroup of numerous small holes in each of the belt members. JP-B HEI05-78713 or JUM-A HEI 05-8139 teaches a means for preventing thecavitation by fitting the valve member on the secondary side thereofwith a rectifying plate. JUM-C 2589805 concerns a butterfly valve whichis intended to repress the cavitation by fitting an eccentrically shapedvalve member on one side thereof with a wing member and forming amultiplicity of small holes in the wing member, and JUM-B HEI 07-43553concerns a butterfly valve which is intended to repress the cavitationby forming small through holes in circular flanges on the opposite sidesof a valve member. JP-A HEI 07-208615 also concerns a valve which isintended to repress the cavitation by forming small holes in each of thelaterally opposite wing members of a valve member.

Since the conventional methods cited above invariably have as their mainobjects the attainment of the prevention of the cavitation by rectifyingthe flow of a fluid, they are substantially incapable of eithereffecting fine adjustment of a fluid in the area of low degree ofopening or the area of minute degree of opening or offering a fullysatisfactory control valve for the adjustment of a flow volume in thearea of low degree of opening or the area of minute degree of opening.Thus, a practicable butterfly valve possessed of an efficientperformance of high range ability has not been realized to date. Such isthe actual state of affairs.

The butterfly valves of the type intended for use in air conditioners,for example, are used in a fully opened state in the summer season whichdemands full use of the air conditioners, whereas they are generallyused as retained in the area of low degree of opening or the area ofminute degree of opening which falls in the range of adjustment of notmore than 40% of the degree of opening in the other seasons. Dependingon the purpose of use, the valves of this type are used frequently forcontrolling the fluid in the area of low degree of opening or the areaof minute degree of opening.

Particularly, many of these butterfly valves are used in a state havingtheir valve seats fitted with an annular rubber seat. When they are usedin the area of low degree of opening or the area of minute degree ofopening, the volumetric flow rate of the fluid is increased because theflow path between the valve member and the rubber seat is narrowed andthis increased volumetric flow rate possibly induces the rubber seat tosuccumb to the so-called phenomenon of erosion.

This invention has been developed for the purpose of solving the variousproblems encountered by the conventional butterfly valves and has forthe object thereof the provision of a butterfly valve which possesses afunction of resisting cavitation, prevents occurrence of erosion as amatter of course, permits fine adjustment of the fluid in the valve inthe area of minute degree of opening or the area of low degree ofopening, manifests a high range ability, and excels in the function ofcontrol and the function of tight shut.

DISCLOSURE OF THE INVENTION

To attain the above object, the present invention provides a butterflyvalve for opening and shutting an interior of an elastic seat ringmounted in a cylindrical valve casing by rotation of a disc valvemember, wherein the butterfly valve comprises a depressing valve partformed at least on a side of an orifice of the valve member and adaptedto make depressing contact with the elastic seat ring in an area of lowdegree of valve opening or in an area of minute degree of valve opening,a void part formed along an outer peripheral edge of the valve member orat a position of a downstream side of the outer peripheral edge, and acommunicating part formed in the valve member or depressing valve partand adapted to form communication from an interior of the void parttoward the downstream side.

The butterfly valve further comprises tight-shut valve shutting partsformed along the outer peripheral edge of the valve member and includinga valve shutting part disposed on the orifice side, and a site of anincreased wall thickness of the valve member between the valve shuttingpart and the depressing valve part, wherein the depressing valve part isformed as directed toward the downstream side of the valve shuttingpart, the void part is disposed at the site of the increased wallthickness, and the communicating part is intended for effecting fluidcontrol.

In the first-mentioned butterfly valve, the depressing valve part isformed in a smaller diameter than the valve member in order that thedepressing valve part may exert a smaller amount of depression on theseat ring than the valve member on the seat ring.

In the first-mentioned butterfly valve, the depressing valve part atleast on the orifice side has formed therein an inflow part foradmitting a fluid from an outer peripheral surface of the depressingvalve part toward the downstream side of the valve member andcontrolling a volumetric flow rate of the fluid.

In the first-mentioned butterfly valve, the depressing valve partcomprises wing-like pieces formed along opposite outer peripheral edgesof the valve member as directed toward a direction of shutting the valvemember and the wing-like pieces have outer peripheral surfaces thereofformed spherically.

A butterfly valve for opening and shutting an interior of an elasticseat ring mounted in a cylindrical valve casing by rotation of a discvalve member, characterized in that a fluid is allowed not to flow froma nozzle side of the valve member but to flow only from an orifice sidethereof to attain high range ability.

In the butterfly valve, an outer peripheral edge of the valve member isprovided on a nozzle side and an orifice side with depressing valveparts formed as directed toward a downstream side and the depressingvalve part on the orifice side has formed therein an inflow part foradmitting the fluid from an outer peripheral surface of the depressingvalve part toward the downstream side and adjusting a volumetric flowrate of an incoming fluid.

A butterfly valve for opening and shutting an interior of an elasticseat ring mounted in a cylindrical valve casing by rotation of a discvalve member, wherein the butterfly valve comprises a depressing valvepart provided along an outer peripheral edge on an orifice side of thevalve member as directed toward a downstream side and an inflow partformed in a neighborhood of the depressing valve part for opening towarda secondary side to enable adjustment of a volumetric flow rate of afluid to be attained with high accuracy in an area of minute degree ofvalve opening.

A butterfly valve for opening and shutting an interior of an elasticseat ring mounted in a cylindrical valve casing by rotation of a discvalve member, wherein the valve member is provided along an outerperipheral edge on a nozzle side and an orifice-side outer peripheraledge with wing-like pieces directed toward a downstream side, withlengths of the wing-like pieces on the nozzle side and the orifice sidevaried to suppress a phenomenon of jumping during break-off of a largestmovable part of the valve member from the elastic seat ring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating one example of the valvemember used in a butterfly valve of this invention.

FIG. 2 is a front view of FIG. 1.

FIG. 3 is a cross section taken through FIG. 2 along line A—A.

FIG. 4 is a plan view of FIG. 2.

FIG. 5 is a cross section illustrating the butterfly valve of thisinvention in the state having the degree of valve opening set at 0%.

FIG. 6 is a cross section illustrating the butterfly valve in the statehaving the degree of valve opening set at 28% and at 100%, i.e. fullopening, in FIG. 5.

FIG. 7 is a graph showing the characteristic of high range abilitymanifested by the butterfly valve of this invention.

FIG. 8 is a graph showing the range of low degree of opening in FIG. 7on a magnified scale.

FIG. 9 is partially magnified cross section illustrating the state ofthe orifice side having the degree of valve opening set at 10%.

FIG. 10 is a partially magnified cross section illustrating the state ofFIG. 9 having the degree of valve opening set at 15%.

FIG. 11 is a partial explanatory diagram showing the degree of valveopening set at 0% for explaining the jumping phenomenon of the valvemember.

FIG. 12 is a partial explanatory diagram illustrating the state havingthe degree of valve opening set at 10% in FIG. 11.

FIG. 13 is a partially magnified cross section illustrating anotherexample of the state shown in FIG. 9.

FIG. 14 is an explanatory cross section illustrating another example ofthe butterfly valve contemplated by this invention.

FIG. 15 is a partially cutaway magnified diagram of the valve membershown in FIG. 14.

FIG. 16 is an explanatory diagram for illustrating the prevention of theoccurrence of cavitation in the valve structure shown in FIG. 15.

FIG. 17 is a partially cutaway magnified diagram of a valve memberdepicting yet another example of the butterfly valve contemplated bythis invention.

BEST MODE OF EMBODYING THE INVENTION

The best mode of embodying this invention will be described in detailbelow with reference to the accompanying drawings.

Referring to FIG. 5 and FIG. 6, the butterfly valve of this example isconstructed by loading an elastic seat ring 2 made of rubber, such asNBR or EPDM, by means of seizure to the inner wall of a cylindricalvalve casing 1 and rotatably disposing a disk-like valve member 3 insidethe seat ring 2 and allowing the valve member 3 to be opened and shut.

Further, as illustrated in FIG. 1, accommodating parts 6 and 7 intendedrespectively for an upper stem 4 and a lower stem 5 are formed at thecentral opposite positions of the valve member 3, and valve shuttingparts 3 a and 3 b formed along the outer peripheral edge of the valvemember 3 are so shaped as to manifest a valve shutting function (tightshut function).

The valve member 3, as illustrated in. FIG. 4, is so formed that thevalve shutting part 3 a on the orifice side is inclined toward theprimary side of the valve at an angle of about 3° relative to the valveshutting part 3 b on the nozzle side. Consequently, the valve shuttingpart 3 a on the orifice side contacts the seat ring 2 with a shallowangle and narrows the range in which it is pressed against the seat ring2 to thereby decrease the amount of its own eating into the seat ring 2.When the valve member 3 is rotated from the position at which the valveis completely shut, therefore, the valve shutting part 3 a on theorifice side immediately parts from the seat ring 2 and begins to adjustthe volumetric flow rate from the low degree of opening while repressingthe occurrence of a sudden motion of the valve member 3, namely theso-called phenomenon of jumping.

The angle of inclination indicated above is preferred to be small forthe purpose of starting the adjustment of the volumetric flow rate fromthe low degree of opening and meanwhile to be large in proportion to thedecrease in the nominal diameter of the valve (for example, 3 in thecase of 100 mm and 7 in the case of 50 mm). This is because in the valveof a small nominal diameter, the radius of the valve member is small andthe width of motion of the valve member is small at the largest movablepart (the position perpendicular to the valve shaft) of the valve memberrelative to the angle of rotation of the valve shaft (stem). This angleof inclination, therefore, is preferred to be in the range of 3 to 7.

Referring now to FIG. 3 and FIG. 4, depressing valve parts 10 and 11 areformed respectively on an orifice side 8 and a nozzle side 9 around thestems 4 and 5 of the valve member 3. The depressing valve parts 10 and11 are brought into depressing contact with the elastic seat ring 2during the retention of the valve member 3 in a low degree of valveopening and consequently enabled particularly to prevent the so-callederosion phenomenon from occurring on the orifice side 8. The term“orifice side 8” refers to the opening part having the valve member 3 onthe upstream side and the term “nozzle side 9” refers to the openingpart having the valve member 3 on the downstream side.

The depressing valve parts 10 and 11 in the present example arewing-like pieces (depressing valve parts) 10 a and 11 a formed along theopposite outer peripheral edges of the valve member 3 as directed towardthe shutting direction of the valve member 3. These wing-like pieces 10a and 11 a possess a function of imparting a depressing contact to theelastic seat ring 2 during the retention of the valve member 3 in thelow degree of opening, and their outer peripheral surfaces are formedspherically so as to establish a spherical contact with the innerperipheral surface of the seat ring 2. Since the wing-like pieces 10 aand 11 a have their pressures balance each other owing to theequilibrium between positive pressure and negative pressure, they areenabled to move the valve member 3 with a light force of manipulationand allay markedly the torque of manipulation of the valve.

As shown in FIG. 4, the expression á<â is satisfied by setting the angleá of the wing-like piece 10 a on the orifice side 8 at 27 and the angleâ of the wing-like piece 11 a on the nozzle side 9 at 30 respectivelywith reference to a valve shutting part 3 b on the nozzle side. Thisexpression is necessary for preventing the fluid from beginning its flowfrom the nozzle side 9 even when the wing-like piece 10 a on the orificeside 8 parts from the seat ring 2 and a falcate flow path (not shown)formed between the orifice side 8 and the seat ring 2 assumes a statefor allowing the fluid to flow, thereby securing the prescribedvolumetric flow rate characteristics (such as, for example, the equalpercent characteristic) through a communicating part 13, inflow ports 14and 15 which will be specifically described herein below and the falcateflow path.

By varying the lengths of the depressing valve parts 10 and 11 on theorifice side 8 and the nozzle side 9 as described above, it is madepossible to prevent further the occurrence of the jumping phenomenon ofthe valve member 3 because one of the depressing valve parts is retainedas depressed on the seat ring 2 while the other depressing valve parthappens to separate from the seat ring 2.

The lengths of the depressing valve parts 10 and 11 are to be set inconsideration of factors, such as control of the volumetric flow rateand repression of the cavitation. This setting varies with the diameterof the valve. The expression of á<â is preferred where the nominaldiameter of the valve is 50 mm, for example. When the degree with whichthe repression of the cavitation is taken into consideration isheightened as when the nominal diameter increased to 150 mm, forexample, the adoption of the expression of á>â may be allowed. Themagnitudes of á and â are only required to satisfy the relation of á âfrom the viewpoint of repressing the occurrence of the jumpingphenomenon of the valve member 3.

In the present example, the diameter ØB of the depressing valve parts 10and 11 and the diameter ØA of the valve member 3 are identical. Thediameter ØB of the depressing valve parts 10 and 11 may be smaller thanthe diameter ØA of the valve member 3 (valve shutting part 3 a) asillustrated in FIG. 11 and FIG. 12. In this case, the amount ofdepression b exerted by the depressing valve parts 10 a and 11 a on theseat ring 2 is smaller than the amount of depression a exerted by thevalve member 3 on the seat ring 2. That is, by giving a smaller size tothe diameter ØB than to the diameter ØA and consequently differentiatingthe quantities of depression exerted on the seat ring 2 to a>b, it ismade possible to decrease the slide resistance on the ØB side inconsequence of the rotation of the valve member 3 and prevent thejumping phenomenon from occurring during the retention of the valvemember 3 in the low degree of opening.

On the orifice side 8 of the valve member 3, a void part (slit) 12 isformed in the outer peripheral edge of the valve member 3 or at aposition on the downstream side of the outer peripheral edge asillustrated in FIG. 1, and the communicating part (communicating hole)13 extending from the void part 12 toward the downstream side is formed.This void part (slit) 12 is provided for the purpose of preventing theoccurrence of the cavitation by attenuating the fluid flowing from theprimary side of the valve via the communicating part 13 to the secondaryside of the valve and keeping the pressure thereof from falling belowthe saturated steam pressure in the area of the minute degree of valveopening (3 to 5 in the present example). With reference to FIG. 9, thevoid part 12 functions as a pressure chamber for enabling an inner wall12 a of the void part 12 to manifest the function of a resistance plate.The width of this void part (slit) 12 is preferred to be large for thepurpose of passing the fluid copiously, but to be small for the purposeof preventing the seat ring 2 from eating into the slit 12. Furthermore,though the optimum size of this slit 12 is variable with the nominaldiameter of the valve, it is set in the range of 3 mm to 10 mm in dueconsideration of the possibility that the slit 12 may be formed duringthe course of casting. The depth of this slit 12 is set in the range of⅓ to ½ of the distance from the largest movable part of the valve memberto the center of the valve member in consideration of the settingoperation of the volumetric flow rate and cast-forming operation.

The communicating part 13 is provided for the purpose of controlling thevolumetric flow rate of the fluid advancing from the primary side of thevalve to the secondary side of the valve in the area of a minute degreeof valve opening. In the present example, four such communicating parts13 are disposed at the site of the largest rotation on the orifice side.The size, shape and quantity of these parts are arbitrarily selected tosuit the actual performance of the disposition. The characteristics ofvolumetric flow rate can be arbitrarily altered through variation in thediameter of holes and the intervals of arrangement.

The communicating part 13, when disposed in the proximity of the bottompart of the slit 12, is enabled to pass the fluid toward the secondaryside of the valve while keeping the interior of the slit 12 in a statefully liberated from the influence of the cavitation. The shape and thequantity of such communicating parts 13 are arbitrarily selected to suitthe characteristic properties of the fluid to be handled. By having thetotal surface area of openings in the communicating part 13 equal orexceed the area of openings in the slit 12 in the outer peripheral partof the valve member, it is made possible to guide the fluid flowing intothe slit 12 efficiently toward the secondary side without requiring thefluid to be unduly squeezed.

In the wing-like piece 10 a on the orifice side 8, a plurality of minuteinflow parts (inflow ports) 14 adapted to advance the fluid from theouter peripheral surface toward the downstream side are disposedradially as illustrated in FIG. 1 and a plurality of minute inflow parts(inflow ports) 14 and a plurality of minute inflow parts 15 both adaptedto advance the fluid from the outer peripheral surface toward thedownstream side are disposed radially as illustrated in FIG. 9 and FIG.13. These inflow parts 14 and 15 are each so disposed as to produce anaction of rectifying the fluid. Incidentally, the minute inflow parts 15are disposed more toward the slit 12 side than toward the minute inflowparts 14 and are intended to exalt the discrimination of the control ofthe volumetric flow rate relative to the angle of rotation of the valveshaft (stem). It is preferred that they are provided for a valve havinga particularly large nominal diameter such as, for example, a nominaldiameter of not less than 200 mm.

These inflow ports 14 and 15 are provided for the purpose of controllingthe volumetric flow rate of the fluid advancing from the primary sidetoward the secondary side in cooperation with the communicating part 13mainly in the area of a low degree of valve opening (5 to 30 in thepresent example).

In the present example, five circular inflow ports (inflow parts) 14 ofone and the same shape are disposed on meridians on the spherical outerperipheral surface of the wing-like piece 10 a at angular intervals of20 degrees around the largest movable part of the valve member 3 asillustrated in FIG. 1 and FIG. 2. When the valve is opened, the fluidbegins to flow simultaneously through the five ports 14 in consequenceof the rotation of the valve member 3. The volumetric flow rates of thefluid through the individual ports 14 become varied with the differencesof their positions in proportion as the degree of opening of the valveincreases.

Since the valve member 3 is not provided on the nozzle side 9 thereofwith any hole for intercommunicating the primary side and the secondaryside of the valve as illustrated in FIG. 4, the fluid in the area of aminute degree of valve opening and the area of a low degree of valveopening wholly flows via the communicating parts 13 and the inflow ports14 provided in the valve member 3 on the orifice side 8. Thus, it ismade feasible to obtain a butterfly valve that permits the volumetricflow rate of a fluid to be accurately controlled even in the area of alow degree of valve opening and materializes high range ability.

In the diagram, the reference numeral 16 denotes each of flange partsfixed to a pipe 17. The butterfly valve-of this example is mountedbetween the flange parts 16 and 16 as nipped with bolts and nuts.

Now, the action of the mode of embodiment described above will beexplained below.

Referring to FIG. 5, when the liquid (fluid), such as water, flows infrom the right side indicated with an arrow mark while the valve member3 remains in a state of complete shut (degree of valve opening: 0%), thevalve shutting parts 3 a and 3 b of the valve member 3 are tightlydepressed on the seat ring 2 made of rubber and allowed to retain acompletely shut state.

In the completely shut state, the nozzle side valve shutting part 3 b istightly depressed in a slightly inclined posture on the seat ring 2, andthe orifice side valve shutting part 3 a is tightly depressed on theseat ring 2 as inclined with a greater angle.

When the valve member 3 is then rotated counterclockwise to a degree ofvalve opening (in the range of 5 to 10%) as illustrated in FIG. 9, theorifice side valve shutting part 3 a separates from the seat ring 2without entailing the jumping phenomenon as described above, and thenozzle side valve shutting part 3 b is subsequently separates from theseat ring 2.

In this case, owing to the fact that the liquid advancing at a minutevolumetric flow rate begins to be rectified from the neighborhood of theorifice side largest rotating part of the valve member 3 onward, thecommunication from the communicating part 13 through the secondary sideof the valve is continued while the occurrence of a vortex or turbulenceis suppressed, and the liquid collides against the inner wall 12 a ofthe void part 12 particularly when it flows into the slit 12 at a minutevolumetric flow rate. As a result, it is made possible to allay theimpetus of the flow of the liquid to such an extent as avoids fallingshort of the saturated steam pressure, inhibit the occurrence of a lowpressure part, suppress the occurrence of cavitation, and keep theoccurrence of noise down. Since the surface area of the opening of thevoid part 12 is increased and the volumetric flow rate is increased abit at a time as the rotation of the valve member 3 is continued, thebutterfly valve is enabled to control the minute volumetric flow rate ofthe liquid with high accuracy and function as a control valve.

Specifically, since the depressing valve part 10 of the valve member 3,namely the wing-like piece 10 a in the present example, makes adepressing contact with the elastic seat ring 2, the liquid isinfallibly passed through the communicating part 13 without escapingbetween the depressing valve part 10 and the elastic seat ring 2. As aresult, the elastic seat ring 2 is not impaired by the so-calledphenomenon of erosion, but is enabled to effect fine adjustment of thevolumetric flow rate of the liquid, depending on the shape of thecommunicating part 13.

Referring to FIG. 11 and FIG. 12, when the degree of valve opening ischanged from 0%, namely the magnitude representing the state of completeshut of the valve, to 10%, since the quantities of the depressing forceexerted by the depressing valve parts 10 and 11 on the seat ring 2 havethe relation a>b, the depressing force exerted by the sphericalwing-like pieces 10 a and 11 a of the depressing valve parts 10 and 11on the inner peripheral surface of the seat ring 2 is weaker than thedepressing force exerted by the valve shutting part 3 a on the seat ring2. In a minute degree of valve opening, the valve member 3 does notbegin to rotate suddenly because the slide resistance offered to therotation of the valve shaft is small. Thus, the degree of valve openingcan be finely adjusted, and the so-called phenomenon of jumping can beinfallibly prevented.

When the degree of valve opening is increased further to 15% asillustrated in FIG. 10, the liquid (fluid) is passed from the largestrotating part of the valve member 3 through the void part 12, rectifiedand released by the communicating part 13, and made to flow in throughthe minute inflow part 15. Since the liquid is rectified and restrainedfrom a vortex or turbulence as well, inhibited from suddenly increasingthe flow velocity, and allowed to prevent the occurrence of alow-pressure part, the cavitation can be prevented from occurring andthe minute volumetric flow rate can be rectified and adjusted.

Even in this degree of valve opening, the liquid infallibly passes thecommunication part 13 and the minute inflow port 15 without leakingbetween the depressing valve part 10 and the elastic seat ring 2 becausethe depressing valve part 10 of the valve member 3 remains in depressingcontact with the elastic seat ring 2. As a result, the control of theminute volumetric flow rate of the liquid depending on the shapes of thecommunicating part 13 and minute inflow part 15 can be accomplishedwithout suffering the elastic seat ring 2 to be impaired by theso-called phenomenon of erosion.

When the degree of valve opening is further increased to 28% asillustrated in FIG. 6, the liquid on the orifice side 8 establishescommunication from the void part 12 through the communicating part 13and flows in radially through the minute inflow parts 14 and 15. Whenthe valve member 3 passes the orifice side 8, therefore, the liquid isinhibited from generating vortex or turbulence on the orifice side,allowed to undergo rectification and secure inflow, repressed frominducing cavitation, prevented from causing erosion, and repressed fromemitting noise and vibration.

In the degree of valve opening illustrated in FIG. 6, though the liquidpasses the space intervening between the depressing valve part 10 andthe elastic seat ring 2, the impairment of the elastic seat ring 2 bythe so-called phenomenon of erosion cannot occur because the liquid isallowed to flow as dispersed to the communicating part 13 and the minuteinflow parts 14 and 15 as well.

Thus, when the valve member 3 is rotated as illustrated in FIG. 5 andFIG. 6, since the spherical wing-like pieces 10 a and 11 a of thedepressing valve parts 10 and 11 are exerting depressing pressure on theinner peripheral surface of the seat ring 2 as described above, thevalve member 3 cannot be suddenly rotated by the repulsive force of theseat ring 2, and the degree of valve opening can be finely adjusted inthe minute degree of valve opening. The butterfly valve, therefore, canprevent the so-called phenomenon of jumping infallibly and can as wellmanifest the function as a control valve that materializes adjustment ofthe volumetric flow rate.

In the case of the butterfly valve which uses a rubber seat, the controlof the volumetric flow rate is generally carried out by adjusting theposition of the valve member in the range of the degree of valve openingof 30 to 70 as clearly noted from the data of comparative examples shownin FIG. 7 and FIG. 8. In contrast, according to the present example,since the adjustment of the volumetric flow rate is realized in therange of 0 to 30 as shown in the diagram, the butterfly valve candecrease the magnitude of Cv as much as possible in the degree of valveopening which is capable of adjusting the volumetric flow rate and canattain high range ability. FIG. 7 is a graph showing the relationbetween the degree of valve opening and the magnitude of Cv and showingthe state of high range ability attained in this invention and servingto demonstrate that the butterfly valve of this invention manifests ahigh range ability characteristic. Incidentally, in this case, thenumerical value of Cv exhibited by the butterfly valve of this inventionfalls below that exhibited by the butterfly valve of the comparativeexample as the valves approach the degrees of full opening. When thebutterfly valve of this invention is used in a feed line of hot water orcold water particularly to an air conditioner, the fall of the magnitudeof Cv actually brings no effect on the actual operation because thebutterfly valve is generally used in a low degree of valve opening.

In the diagram, the data are invariably those obtained of the sampleshaving a nominal valve diameter of 100 mm and using valve members madeof SCS13A. The data of the comparison are those obtained of butterflyvalves using a known central type valve member that forms neither a flowpath port nor a wing-like part. The seat ring and other parts formed inthis conventional valve member are similar to those used in the valvemember of the butterfly valve of this invention.

The comparative sample indicated in the diagram is capable of accuratelycontrolling the volumetric flow rate in the degrees of valve openingapproximately in the range of 30% to 80% and manifesting range abilityof 10:1. In contrast, the sample of the prevent invention isdemonstrated to be capable of accurately controlling the volumetric flowrate in degrees of valve opening approximately in the range of 10% to100% and manifesting a high range ability characteristic of 200:1.

FIG. 13 illustrates another example of the butterfly valve to which thisinvention relates. Like parts used in the preceding example will bedenoted by like reference numerals and omitted from the followingdescription. In the construction shown in the diagram, a plurality offlow path holes 13 a are provided instead of the slit and, through thecommunicating parts (flow path holes) 13 a, the butterfly valve of thisconstruction admits the inflow of the fluid, permits adjustment of thevolumetric flow rate, and fulfills substantially the same function andeffect as the preceding example.

FIG. 14, FIG. 15 and FIG. 16 illustrate another example of the valvemember contemplated by this invention. In this construction, slits 19and 20 are formed in the outer periphery of a valve member 18 andcommunicating holes 21 and 22 are further formed so as to effectrectification of the fluid, prevent the occurrence of a low pressurepart on the rear stream side of the valve member 18, suppress thecavitation, and render it possible as well to control the volumetricflow rate in the area of a low degree of valve opening. In this case,the communicating holes 21 and 22 are so formed as to give a greaterdiameter to the former hole 21 than to the latter hole 22 and enable thevolumetric flow rate to increase in accordance as the degree of valveopening is enlarged.

Further, by forming the slits 19 and 20 so as to give a larger size tothe former slit 19 than to the latter slit 20, it is made possible toattenuate the fluid pressure stepwise and prevent the occurrence of thecavitation. Specifically, by establishing the relation of slit 19>slit20 as illustrated in FIG. 15 and FIG. 16, the occurrence of thecavitation is prevented by keeping the pressure of the fluid fromfalling below the saturated steam pressure.

FIG. 17 illustrates yet another example of the valve member contemplatedby this invention. It is provided with slits 24, 25 and 26 andcommunicating holes 27, 28 and 29. Of course, this example manifests thesame function and effect as the other examples cited above.

By disposing a strainer on the upstream side of the butterfly valve ofeach of the examples of this invention and utilizing it as a componentof the relevant valve system, it is made possible to guide the liquiddeprived of foreign matter by the strainer to the butterfly valve ofthis invention and prevent the communicating part 13 and the inflowparts 14 and 15 from being clogged and allow the control of thevolumetric flow rate with high accuracy to be continued.

Industrial Applicability

According to this invention, there is provided a butterfly valve whichis capable of producing tight shut due to the use of an elastic seatring, preventing the elastic seat ring from yielding to the phenomenonof erosion, and realizing prominently high range ability as comparedwith the conventional butterfly valve.

By substituting the valve member of this invention in a butterfly valveusing the ordinary seat ring, the butterfly valve may be utilized as acontrol valve that can be used in a low degree of valve opening.

This invention can further provide a butterfly valve that is aninexpensive control valve which is capable of assigning a wide range forthe adjustment of volumetric flow rate properties, such as an equalpercent characteristic, allaying noise, and suppressing torsion.

Since the valve member is formed as inclined, the control valve isenabled to suppress the phenomenon of jumping, namely a sudden motion ofthe valve member and begin the adjustment of the volumetric flow ratewhen the valve member is set to rotating from the position of completeshut.

By varying the length of the depressing valve part on both the orificeside and the nozzle side, it is made possible to prevent the valvemember infallibly from developing the phenomenon of jumping even wheneither of the depressing valve parts happens to separate from the seatring because the other depressing valve part is retained in a state ofbeing depressed on the seat ring.

What is claimed is:
 1. A butterfly valve for opening and shutting aninterior of an elastic seat ring mounted in a cylindrical valve casingby rotation of a disc valve member, wherein the butterfly valvecomprises valve shutting part formed along an outer peripheral edge ofthe valve member on an orifice side and on a nozzle side to create tightshut, depressing valve parts formed on the valve shutting parts andadapted to make depressing contact with the elastic seat ring toward ashutting direction of the valve shutting parts, a void part formedbetween the depressing valve part on the orifice side and the valveshutting part on the orifice side, and a communicating part formed inthe valve member and adapted to establish communication from an interiorof the void part toward downstream side, thereby allowing a fluid not toflow from the nozzle side of the valve member but to flow only from theorifice side thereof, to attain high range ability in an area of lowdegree of valve opening or in an area of fine degree of valve opening.2. The butterfly valve according to claim 1, further comprises thetight-shut valve shutting parts formed along the outer peripheral edgeof the valve member and including said valve shutting part disposed onthe orifice side, and a site of an increased wall thickness of the valvemember between the valve shutting part and the depressing valve part,wherein the depressing valve part is formed as directed toward thedownstream side of the valve shutting part, the void part is disposed atthe site of the increased wall thickness, and the communicating part isintended for effecting fluid control.
 3. The butterfly valve accordingto claim 1, wherein the depressing valve part is formed in a smallerdiameter than the valve member in order that the depressing valve partmay exert a smaller amount of depression on the seat ring than the valvemember on the seat ring.
 4. The butterfly valve according to claim 1,wherein the depressing valve part on the orifice side has formed thereinan inflow part for admitting the fluid from an outer peripheral surfaceof the depressing valve part toward the downstream side and controllinga volumetric flow rate of an incoming fluid.
 5. The butterfly valveaccording to claim 1, wherein the depressing valve part compriseswing-like pieces formed along opposite outer peripheral edges of thevalve member as directed toward a direction of shutting the valve memberand the wing-like pieces have outer peripheral surfaces thereof formedspherically.
 6. A butterfly valve for opening and shutting an interiorof an elastic seat ring mounted in a cylindrical valve casing byrotation of a disc valve member, wherein the butterfly valve compriseswing-like depressing valve parts provided along an outer peripheral edgeof the valve member on an orifice side and on a nozzle side, havingouter peripheral surfaces formed spherically toward the downstream side,and adapted for depressing contact with the elastic seat ring in an areaof minute degree of valve opening, and a fluid path port formed in aneighborhood of the depressing valve part on the orifice side andopening into a secondary side of the butterfly valve, thereby permittinga volumetric flow rate of a fluid to be adjusted with high accuracy inthe area of minute degree of valve opening.
 7. A butterfly valve foropening and shutting an interior of an elastic seat ring mounted in acylindrical valve casing by rotation of a disc valve member, wherein thebutterfly valve comprises wing-like pieces provided along an outerperipheral edge of the valve member on a nozzle side and on an orificeside as directed toward a downstream side, with lengths of the wing-likepieces on both the nozzle side and the orifice side varied to enable oneof the wing-like pieces to retain a state of being depressed on theelastic seat ring while the other wing-like piece tends to separate fromthe elastic seat ring and consequently suppress the valve member fromdeveloping a phenomenon of jumping in an area of low degree of valveopening or in an area of minute degree of valve opening.